SIEMENS C3m POST OFFICE TRIODES 1960S SUPERVALVE USED TESTED
- Highest amplification
- Lowest low noise
- Lowest microphonic
- Greater lifetime than commercial tubes
- Stand-by possibility
- Metal shielding
- Use triode connected with loss of gain but no distortion increase
- Comprehensive data sheet
- Optional: Individual series number on each tube
- Zirconium getter blade incorporation for dynamic gas sorption.
The cost of these paragons of thermionic perfection in 1965 was 295DM…. which equates £100, all at a time when for the price of 30 of these fine valves, you could buy a decent semi!!!!!!!
Some users do not like their closed can shielded appearance, however, with a bit of care both the black shield and the base overlap can be removed leaving a valve that looks a little like an EF86 on steroids
Generally with C3m and C3g it can be said they have the gain of a pentode, and distortion levels similar to the finest triodes at more than three times the level of gain. As an example a C3m with a gain of 78 allows driving of a 300B with less than 1V input sensitivity with 0.12% THD. In a few words - these are superb valves for hifi usage.